1. Field
Example embodiments of the following description relate to an image sensor based on a depth pixel structure, and more particularly, an image sensor having a pixel structure that may sense depth information based on Time-of-Flight (TOF).
2. Description of the Related Art
A method of acquiring information regarding a distance from a sensor to an object may be broadly classified into an active scheme and a passive scheme. The active scheme may typically include a Time-of-Flight (TOF) scheme of measuring a travel time of a light by detecting the light radiated to an object and reflected and returned from the object, and a triangulation scheme of detecting a location of a light radiated and reflected from an object by a laser spaced by a predetermined distance from a sensor, and of calculating a distance to the object using a triangulation. The passive scheme may typically include a scheme of calculating a distance to an object based on only image information, not radiating a light, and may be employed in a stereo camera.
In a distance measurement scheme as described above, a TOF-based sensor may be advantageous in acquiring a depth image in real time. In particular, a scheme of obtaining a TOF is being widely used by radiating a modulated light having a predetermined frequency and a predetermined waveform, and by demodulating a light reflected from an object in a detector.
To perform demodulation indispensable for a TOF, a generated electron is required to be transferred within an extremely short period of time in a photodiode. Accordingly, there is a desire for a method that may efficiently, inexpensively fabricate a structure for transferring an electron within an extremely short period of time in a photodiode.